I've actually used a remote controlled egg vibrator with my girlfriend at parties and other public events. Here is what I've learned:
1) The egg, when activated, makes a fairly loud and distinct sound like all vibrators. It may be inside her, but if you're anywhere without music or moderately loud ambient sound, people close by (within talking range) will likely here it. This can be...awkward.
2) When out at a party, drinking with friends, it's hard not to share with others that you have a remote that can set your SO's vagina to buzzing from 20yrds away. Yes, it's kinda hot when her female friends want to "hold" the remote. No, she was not cool with me letting my mates get a hold of the remote.
3) This can still be a really hot toy. My SO said she liked The Egg because she new it meant I was thinking about her all night. Even if I wasn't in her line of sight, that buzz meant I was thinking of her pleasure. Going out with The Egg usually meant going home early and fucking our brains out, sans Egg. The downside, it didn't really have much of a stimulating effect for her in the immediate, and if it did, she probably wouldn't have been all that willing to where it in public, just too distracting.
4) The most fun we had with The Egg was during oral or anal sex. And during these sessions she would hold the remote more often than I. She knows her rhythms better, not to mention it leaves my hands free for more important things.